<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <link rel="stylesheet" href="./css/3.css">
</head>
<body>
    <!--
        flex布局
        特点：自适应
    -->
    <section class="layout flex">
        <article>
            <p>3.flex<br>（自适应）</p>
        </article>
    </section>
</body>
</html>